CMP: Chemical Mechanical Polishing
DRIE: Deep Reactive Ion Etching
IMCS: Integrated Micro Coil Structure
MEMS: Micro Electro Mechanical System
MRI: Magnetic Resonance Imaging
NMR: Nuclear Magnetic Resonance
Pixel: picture element
PECVD: Plasma-Enhanced Chemical Vapor Deposition
RIE: Reactive Ion Etching
RF: Radio Frequency
SNR: Signal to Noise Ratio
3D: three-dimensional
UV LIGA: Ultra Violet LIGA
Voxel: volume element
This invention relates to the field of Magnetic Resonance Imaging (MRI). Specifically, the present invention is directed to an array of vastly miniaturized MRI structures and method of its manufacturing for a new MRI system with very high resolution down to the sub-micron range.
MRI has offered a powerful, non-intrusive 3D imaging technique for various medical, engineering and scientific studies. This is achieved by spatially coding the precessing frequencies or phases of nuclear magnetic moments of a sample under study under a bias magnetic field, typically 0.5 Tesla to 10xe2x80x2s of Tesla, and using Radio Frequency (RF) coils to excite and detect emitted signals with a certain sequence. A three-dimensional (3D) image is then reconstructed after signal processing with a processor. For medical diagnosis, a resolution of a few millimeters is typically adequate. However, if the subject under study is an organ of a small animal, then a Nuclear Magnetic Resonance (NMR) microscope is required. The resolution of current MRI is limited in practice from going below a few millimeters for medical imaging, or below a few micrometers for NMR microscopy or micro MRI imaging.
In many medical and scientific studies, it is desirable to have the ability to perform 3D imaging to track magnetic or magnetically labeled nano-sized elements or molecules, or to be able to look into cell to cell interaction, cell cycles, embryo cells, cancer cells development, cell infection or toxicity response etc. However, when it comes to small samples such as a small cluster of cells or even a single cell, a sub-micrometer imaging resolution is needed. For small samples, the MRI resolution is typically limited by the ability of the gradient coils to generate a large enough and uniform magnetic field gradient for the receiving system to have enough signal to noise ratio since the total magnetic moment responsible for generating certain frequency signal scales with the pixel volume. While averaging with multiple measurements can reduce the level of uncorrelated noise with the square root of the number of measurements, the cost of the resulting measurement time becomes prohibitive.
The inability to generate a large enough magnetic field gradient also limits the ability to manipulate small magnetic moments. To exert a sufficient net force on small magnetic particles/molecules, for sorting, manipulation etc., requires the ability to generate a large enough magnetic field gradient as the net force acted on a magnetic moment is proportional to the magnetic field gradient.
In essence, it is desirable to develop new systems capable of sub-micrometer imaging resolution for MRI and capable of manipulating small magnetic moments of nanometer-sized particles.
The first object of this invention is to achieve a new MRI system capable of sub-micrometer imaging resolution.
The second object of this invention is to batch-manufacture such a new MRI system with low cost.
A third object of this invention is to have such new MRI system capable of manipulating small magnetic moments.
Other objects, together with the foregoing are attained in the exercise of the invention in the following description and resulting in the embodiment illustrated in the accompanying drawings.